NSFileManager相关
枚举相同格式的文件：
You can achieve this pretty easily with the help of NSPredicate, like so:

NSString *bundleRoot = [[NSBundle mainBundle] bundlePath];NSFileManager *fm = [NSFileManager defaultManager];NSArray *dirContents = [fm contentsOfDirectoryAtPath:bundleRoot error:nil];NSPredicate *fltr = [NSPredicate predicateWithFormat:@"self ENDSWITH '.jpg'"];NSArray *onlyJPGs = [dirContents filteredArrayUsingPredicate:fltr];

Checking for file existence:

+(BOOL)fileExistsAtAbsolutePath:(NSString*)filename {    BOOL isDirectory;    BOOL fileExistsAtPath = [[NSFileManager defaultManager] fileExistsAtPath:filename isDirectory:&isDirectory];    return fileExistsAtPath && !isDirectory;}

Checking for directory existence:

+(BOOL)directoryExistsAtAbsolutePath:(NSString*)filename {    BOOL isDirectory;    BOOL fileExistsAtPath = [[NSFileManager defaultManager] fileExistsAtPath:filename isDirectory:&isDirectory];    return fileExistsAtPath && isDirectory;}